"cowardly," 1900, from gut (n.) in the figurative "spirit" sense (see guts) + -less. Literal sense "disemboweled" is from c. 1600. Related: Gutlessly; gutlessness.
Entries linking to gutless
guts n.
"spirit, courage," 1893, figurative plural of gut (n.). The idea of the bowels as the seat of the spirit goes back to at least mid-14c. (compare bowel).
-less
word-forming element meaning "lacking, cannot be, does not," from Old English -leas, from leas "free (from), devoid (of), false, feigned," from Proto-Germanic *lausaz (cognates: Dutch -loos, German -los "-less," Old Norse lauss "loose, free, vacant, dissolute," Middle Dutch los, German los "loose, free," Gothic laus "empty, vain"), from PIE root *leu- "to loosen, divide, cut apart." Related to loose and lease.